Power system configuration

ABSTRACT

A power system includes an input power port, a power rail, a battery unit, and a system charger voltage regulator (VR). The system charger VR couples the input power port to the battery unit. The battery unit couples with the system charger VR and the power rail.

FIELD OF THE INVENTION

The present invention relates to the field of power systems. Morespecifically, the present invention relates to a power systemconfiguration.

BACKGROUND

Many electronic devices can be powered by more than one power source.For example, mobile devices, like notebook computers, can usually beplugged into an AC electric outlet or operated on battery power. Thesekinds of electronic devices usually include some sort of power system toselect from among the available power sources.

FIG. 1 illustrates one example of a typical power system that may befound in any number of electronic devices, such as a notebook computer.An external AC power source 115 is optional. That is, the device may ormay not be plugged into an electric outlet at any particular time. AnAC/DC converter 110 can convert the AC power (if it is available) to anunregulated, or loosely regulated, DC voltage 180. The DC voltage 180 isunregulated, or loosely regulated, in that converter 110 may notactively control the voltage. Instead, converter 110 may be a passivefilter or transformer.

Any number of devices can be used for converter 110. The most familiarkinds of AC/DC converters are rather large blocks that are part of apower cord or power plug. A typical unregulated voltage for a notebookcomputer is about 20 volts.

The power system also includes two additional power sources, batterypack 140 and battery pack 150. Battery packs 140 and 150 each provide abattery voltage 190. Any number of battery pack designs can be used. Atypical battery pack for a notebook computer may include six batterycells coupled in two parallel groups of three cells in series. The safevoltage range for an individual lithium cell is often about 3 to 4.2volts. That is, a fully charged lithium battery cell will typicallyprovide about 4.2 volts, and the voltage will fall off to about 3 voltsas the battery discharges. With three lithium cells in series, a batterypack will often provide a safe voltage range of about 9 to 12.6 volts.Other power systems may include more battery packs or just one batterypack. Other typical battery packs may include different combinations orconfigurations of battery cells. And, other battery cell chemistries canbe used and can provide different voltage ranges.

Source selector 160 selects from among the available power sources basedon switch control signal 107. That is, either the unregulated voltage180 or the battery voltage 190 from one or both of the battery packs canbe coupled to the power rail 170 at any particular time. In which case,for a typical notebook computer, the rail voltage 195 can range fromabout 9 to 20 volts. Power rail 170 can supply power to a wide varietyof components and circuits within the electronic device (not shown).

The illustrated example also includes a battery charger 120 and acharging selector 130. Charger 120 can generate a battery voltage 190from the unregulated voltage 180 (if available). Charging selector 130can supply the battery voltage 190 to recharge either battery pack 140or battery pack 150 based on switch control signal 105.

The switch control signals 105 and 107 can come from any number ofsources. For example, in a notebook computer, an operating system maygenerate the control signals. Whatever the source is for the controlsignals, it may detect when AC power is available, as well as monitorthe power levels of the battery packs, to generate the appropriatecontrol signals. Any number of approaches can be used to select whichbattery to recharge and which power source to use at any given time.

BRIEF DESCRIPTION OF DRAWINGS

Examples of the present invention are illustrated in the accompanyingdrawings. The accompanying drawings, however, do not limit the scope ofthe present invention. Similar references in the drawings indicatesimilar elements.

FIG. 1 illustrates a typical power system configuration.

FIGS. 2-6 illustrate various embodiments of a novel power systemconfiguration.

FIG. 7 illustrates a typical battery pack configuration.

FIG. 8 illustrates one embodiment of a novel battery pack configuration.

FIG. 9 illustrates one embodiment of switch circuitry.

FIG. 10 demonstrates one embodiment of a novel power systemconfiguration.

FIG. 11 demonstrates one embodiment of a novel battery packconfiguration.

FIG. 12 illustrates one embodiment of a hardware system that can performvarious functions of the present inventions.

FIG. 13 illustrates one embodiment of a machine readable medium to storeinstructions that can implement various functions of the presentinventions.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description, numerous specific details are setforth in order to provide a thorough understanding of the presentinvention. However, those skilled in the art will understand that thepresent invention may be practiced without these specific details, thatthe present invention is not limited to the depicted embodiments, andthat the present invention may be practiced in a variety of alternativeembodiments. In other instances, well known methods, procedures,components, and circuits have not been described in detail.

Parts of the description will be presented using terminology commonlyemployed by those skilled in the art to convey the substance of theirwork to others skilled in the art. Also, parts of the description willbe presented in terms of operations performed through the execution ofprogramming instructions. As well understood by those skilled in theart, these operations often take the form of electrical, magnetic, oroptical signals capable of being stored, transferred, combined, andotherwise manipulated through, for instance, electrical components.

Various operations will be described as multiple discrete stepsperformed in turn in a manner that is helpful for understanding thepresent invention. However, the order of description should not beconstrued as to imply that these operations are necessarily performed inthe order they are presented, nor even order dependent. Lastly, repeatedusage of the phrase “in one embodiment” does not necessarily refer tothe same embodiment, although it may.

Two related inventions are described herein. Embodiments of the firstinvention include novel power system configurations that can provide avariety of advantages over prior power systems. Embodiments of thesecond invention include novel battery pack configurations. Embodimentsof the second invention can be used in concert with a variety of powersystems, including embodiments of the first invention.

Although the present inventions are primarily described below in thecontext of a notebook computer, embodiments of the present inventionscan be used in a variety of electronic devices such as video cameras,hand-held computing devices, cellular phones, computer tablets, etc.

FIGS. 2 through 6 illustrate various embodiments of the first invention,the power system configuration. Rather than supplying either anunregulated voltage or a battery voltage to power a electronic device,the illustrated embodiments use the same regulated voltage forrecharging batteries to also power the electronic device. For example,as discussed in the background, a typical power system for a notebookcomputer may provide 9 to 20 volts. By using a regulated voltage to bothpower an electronic device and recharge its batteries, embodiments ofthe present invention can reduce that voltage range. In the case of theexample notebook computer, the voltage range may be reduced to 9 to 12.6volts, or whatever the equivalent of the battery voltage range happensto be. Reducing the voltage range can substantially simplify and reducethe cost of many circuits and components within a typical electronicdevice.

FIG. 2 illustrates one embodiment of the novel power systemconfiguration at a high level. An input power port 210 can be coupled toa power source 270. The power source is optional in that it may or maynot be coupled to the input power port at any particular time. Powersource 270 and input power port 210 are intended to represent any of awide variety of such devices. For example, power source 270 could be anAC power outlet or an AC generator, and port 210 could be an AC/DCconverter. On the other hand, power source 270 could be any of a widevariety of DC power sources, such a solar panel, a fuel cell, or powerover a local area network (LAN). In which case, power port 210 maysimply be a connector between the power source 270 and the rest of thepower system.

In any case, an unregulated voltage 250 can be supplied to a systemcharger voltage regulator (VR) 220. VR 220 can provide a regulatedvoltage 260 when the unregulated voltage 250 is available. Regulatedvoltage 260 can be supplied to battery unit 230. Battery unit 230 iscoupled to power rail 240. Either the regulated voltage 260 or a batteryvoltage (not shown) from battery unit 230 can be provided on the powerrail 240 as rail voltage 280. In other words, regulated voltage 260 canbe used to power the power rail 240 and/or power the battery unit 230 torecharge a battery. The range of regulated voltage 240 can be equal tothe range of the battery voltage provided by battery unit 230. Forexample, the bounds of the voltage range could be 9 to 12.6 volts forboth the regulated voltage 240 and the battery voltage. Any number ofcircuits that can satisfy the requisite power needs can be used forsystem charger VR 220.

FIG. 3 illustrates another embodiment of the novel power systemconfiguration with a single battery and a source selector. Many of thecomponents in FIG. 3 can be the same as those described in FIG. 2 withthe exception of battery unit 330. Battery unit 330 includes a sourceselector 332 and a battery pack port 334. Battery pack port 334 canreceive a removable battery pack 336. In other embodiments, the batterypack may not be removable.

When a battery pack 336 is coupled to port 334, and the battery pack isadequately charged, port 334 can provide a battery voltage 338 to sourceselector 332. Source selector 332 can select between the regulatedvoltage 260 and the battery voltage 338 in any number of ways. Forexample, as described above in FIG. 1, the selection may be based on acontrol signal.

Regulated voltage 260 is supplied to both source selector 332 andbattery pack port 334 in FIG. 3. In which case, the regulated voltagecan simultaneously power the power rail 240 and recharge a dischargedbattery pack 336.

FIG. 4 illustrates another embodiment of the novel power systemconfiguration with multiple batteries and a source selector. Many of thecomponents can be the same as those described in FIG. 2 with theexception of battery unit 430. Battery unit 430 includes a sourceselector 460, a charging selector 430, and two battery pack ports 440and 450.

The battery pack ports 440 and 450 can receive removable battery packs442 and 452. At any particular time, one or both of the battery packports may not have a battery pack installed. In other embodiments, oneor both of the battery packs may not be removable. Other embodiments mayinclude three or more battery pack ports and battery packs.

Source selector 460 can select from among the regulated voltage 250 anda battery voltage 490 from any one of the battery pack ports 440 and 450to provide on power rail 270. Charging selector 430 can supply theregulated voltage 250 to the battery pack ports 440 and 450 to rechargea discharged battery pack. Any number of approaches can be used toselect none, one, or many of the battery packs for recharging. Forexample, as described above in FIG. 1, the selection may be based on acontrol signal.

FIG. 5 illustrates another embodiment of the novel power systemconfiguration with a common power rail and a switched battery unit.Input power port 210 and system charger VR 220 can be the same asdescribed in FIG. 2. Power rail 540, however, is coupled directly tosystem charger VR 220. Battery unit 530 is coupled to VR 220 throughpower rail 540. Battery unit 530 includes a switch 532 and a batterypack port 534. Battery pack port 534 can receive a removable batterypack 536. In other embodiments, battery pack 536 may not be removable.

If power source 270 is coupled to input power port 210, system chargerVR 220 can provide a regulated voltage on power rail 540. If there is abattery pack in battery unit 530, and the battery pack is discharged,switch 532 can couple battery pack port 534 to power rail 540 torecharge the battery. In other words, system charger VR 220 can powerboth battery unit 530 and power rail 540 simultaneously with oneregulated voltage, rail voltage 280.

If power source 270 is not available, there is a battery pack in batteryunit 530, and the battery is not completely discharged, switch 532 cancouple battery pack port 534 to power the power rail 540 with a batteryvoltage. Any number of approaches can be used to control switch 532,such as the control signals described above in FIG. 1. Other embodimentsmay include battery pack ports and switches for two or more batterypacks.

FIG. 6 illustrates another embodiment of the novel power systemconfiguration using one embodiment of the novel battery packconfiguration. The illustrated embodiment is similar to the one shown inFIG. 5 except that battery unit 630 does not include switch 532.Instead, the battery pack port 634 in battery unit 630 includes aswitching control port 638 to supply switching control signals to abattery pack 636. In other words, the switching function is performedwithin the battery pack 636 based on control signals from the batterypack port. The switching function may be the same as the functiondescribe above for switch 532. That is, the battery pack may connectitself to the power rail 540 to either recharge itself or power thepower rail. Any number of approaches can be used to generate the controlsignals.

FIG. 7 illustrates an example of a typical battery pack 700 that couldbe used in a wide variety of electronic devices, such as a notebookcomputer. The illustrated example could also be used with certainembodiments of the novel power system described above, such as theembodiments of FIGS. 3, 4, and 5 in which the power system includes asource selector or battery unit switch.

Some types of battery cells can be dangerous if they are over-charged ordischarged too much. These battery cells can leak corrosive chemicals,generate dangerously high temperatures, or even explode. In which case,battery packs for electronic devices often include some form ofprotection circuitry.

For example, as shown in FIG. 7, in addition to a battery stack 720,battery pack 700 includes a switch 710, a sensor 730, and a batterycontroller 740. The sensor 730 can sense the temperature and currentlevel of battery stack 720. Other embodiments may not sense temperature,may sense voltage instead of or in addition to current, and may senseany of a number of other battery characteristics.

Feedback 735 from sensor 730 is provided to battery controller 740.Based on the feedback, controller 740 can open the switch 710 before adangerous condition develops. Opening switch 710 breaks the circuitbetween the power ports 750 and 755, preventing further charging ordischarging of the battery stack 720.

Any number of switch circuits can be used for switch 710. In theillustrated embodiment, switch 710 comprises back-to-backmetal-oxide-semiconductor field effect transistors (MOSFETs), Q1 and Q2.The source S of Q1 is coupled to the positive output power port 750. Thedrain D of Q1 is coupled to the drain D of Q2. The source S of Q2 iscoupled to the battery stack 720. The gates G of Q1 and Q2 are coupledto the output of battery controller 740. In other embodiments, theswitch can be placed anywhere in the circuit between the positive outputpower port 750 and the negative output power port 755.

Battery controller 740 may also generate various battery status signalsor otherwise communicate with an external system through communicationport 760. For example, a standard called the System Management (SM) BusProtocol defines various types of communication between a battery packand an external system.

FIG. 8 illustrates one embodiment of the novel battery packconfiguration. Many of the components can be the same as those in FIG. 7with the exception of the switch circuitry 840 and a switching controlport 860 in addition to, or in place of, the communications port 760.Control signals for switch 710 can be received over port 860. Switchcircuitry 840 includes switching logic 844 that can couple and decouplethe battery stack using switch 710 based on the switching controlsignals.

In other words, embodiments of the novel battery pack configuration cantake advantage of many of the components found in typical battery packsto perform the switching functions that are often performed in the powersystems of electronic devices. By moving the switching functions to thebattery pack itself, the power systems can be substantially simplified.For example, a comparison of FIG. 1 and FIG. 6 shows that both thecharging selector 130 and source selector 160 can be removed from thepower system, while adding relatively little circuitry to the batterypack.

In addition to switching logic 844, the illustrated embodiment includesprotection circuitry 842 that can perform functions similar to those ofbattery controller 740 from FIG. 7. That is, protection circuitry 842can open switch 710 based on feedback 735 from sensor 730, as well aspotentially communicate with an external system over communications port760. Some embodiments may include a single port for both switchingcontrol signals and other external communications.

Switch circuitry 840 may include any of a number of circuits to performa wide variety of functions. FIG. 9 illustrates just one embodiment ofwhat might be included in switch circuitry 840. In the illustratedembodiment, feedback signal 735 from the sensor 730 is supplied to acomparator 920 and compared to a reference 910. For example, reference910 may be a minimum current level at which the battery stack can safelybe used. If feedback 735 is above this minimum safe bound, comparator920 may set enable signal 930 high. If feedback 735 drops below theminimum safe bound, comparator 920 may set enable signal 930 low. Switchcircuitry 840 may include additional circuitry to similarly test for amaximum safe current level, a maximum safe temperature, etc.

The enable signal 730 may be provided to an external system in the formof a battery status signal 970. In other embodiments, the battery statussignal may be based on a combination of signals. For example, if themaximum current level and maximum temperature are also monitored asmentioned above, the status signal may be a logical AND of all threeenable signals.

Referring back to FIG. 9, enable signal 930 is provided to logical AND950. The other input of AND 950 is coupled to receive a control signalfor switching the battery pack's switch. For example, in the illustratedembodiment, the battery pack receives two switch control signals 905 and907. In a typical power system, such as the system of FIG. 1, whensignal 905 is high it may indicate that a charging selector is supposedto recharge the battery pack, and when signal 907 is high it mayindicate that a source selector is supposed to power the power rail withthe battery pack. Signals 905 and 907 may be, for instance, generated byan operating system.

In the illustrated embodiment, signals 905 and 907 are supplied to thebattery pack rather than a charging selector and a source selector. Inthe battery pack, the signals are combined by logical OR 960. If eithersignal is high, the output of OR 960 will be high, indicating that thesystem requests the battery stack to be coupled to the power rail. Inother words, the illustrated battery pack can be used with an existingoperating system, without changing how the control signals aregenerated.

In other embodiments, the control signals may be combined outside thebattery pack. For instance OR 960 could be located somewhere within apower system rather than in the battery pack, or the signals could becombined in software.

AND 950 combines the enable signal 930 with the output from OR 960 togenerate a gate control signal 940 for switch 710. When the gate controlsignal 940 is high, gate 710 can close and couple the battery stack tothe power output ports. The enable signal 930 acts as a priorityfail-safe. That is, if the enable signal goes low, the output of AND 950will stay low no matter what happens on the switching control signals.

FIG. 10 demonstrates a process for one embodiment of the novel powersystem configuration. At 1010, the process monitors changes in anexternal power source. If an external power source becomes unavailable,the process provides a battery voltage to the power rail at 1040. Thiscould involve, for instance, generating appropriate control signals fora source selector or a battery pack switch. It may also involveselecting from among a combination of one or more available batteries.

If an external power source becomes available at 1010, the processgenerates a regulated voltage at 1020. Then, at 1030, the processprovides the regulated voltage to simultaneously power both a batteryunit and the power rail. Powering the battery unit may involvedetermining if one or more batteries need to be recharged, generatingappropriate control signals to select a battery for recharging, and thenrecharging the selected battery. Any number of approaches can be used toprioritize among one or more batteries and to generate the appropriatecontrol signals.

FIG. 11 demonstrates a process for one embodiment of the novel batterypack configuration. At 1110, the process senses temperature and/orcurrent feedback from a battery stack. At 1120, the process generates abattery status signal based on the feedback and communicates that statussignal to the battery pack port.

The battery status signal is also used internally by the battery pack at1130 to determine if the battery should be disabled. If the batteryshould be disabled, the process opens the switch in the battery pack at1140 and then ends. In some embodiments, a battery stack may bepermanently disabled in this way. In other embodiments, a battery stackmay recover, possibly depending on the type of event that disabled thebattery stack.

If the status signal does not disable the battery stack at 1130, theprocess receives a switch control signal from the battery pack port at1150, and considers the switch control signal at 1160. If the signalindicates that the switch should be closed, the process couples thestack to the output port at 1170. With the switch closed, the batterypack can either be recharged by the power rail or supply power to thepower rail. On the other hand, if the signal indicates that the switchshould be open at 1160, the process decouples the stack at 1180. Ineither case, the process then returns to 1110 to start over.

FIGS. 2-6 and 8-11 illustrate a number of implementation-specificdetails. Other embodiments may not include all of the illustratedelements, may include additional elements, may arrange elements in adifferent order, may combine one or more elements, and the like. Forexample, other battery pack embodiments may not include communicationsport 760, or may combine the functions of communications port 760 andswitching control port 860 into a signal port. Each port in the Figuresmay take any of a variety of forms. For instance, each port may compriseone or more pins, contacts, sockets, etc. Furthermore, any of a numberof alternate hardware circuits can be used to perform the variousfunctions described above. Or, one or more of the functions describedabove may be performed by code executed in a processor.

For example, FIG. 12 illustrates one embodiment of a generic hardwaresystem intended to represent a broad category of computer systems suchas personal computers, workstations, and/or embedded systems. In theillustrated embodiment, the hardware system includes processor 1210coupled to high speed bus 1205, which is coupled to input/output (I/O)bus 1215 through bus bridge 1230. Temporary memory 1220 is coupled tobus 1205. Permanent memory 1240 is coupled to bus 1215. I/O device(s)1250 is also coupled to bus 1215. I/O device(s) 1250 may include adisplay device, a keyboard, one or more external network interfaces,etc.

Certain embodiments may include additional components, may not requireall of the above components, or may combine one or more components. Forinstance, temporary memory 1220 may be on-chip with processor 1210.Alternately, permanent memory 1240 may be eliminated and temporarymemory 1220 may be replaced with an electrically erasable programmableread only memory (EEPROM), wherein software routines are executed inplace from the EEPROM. Some implementations may employ a single bus, towhich all of the components are coupled, or one or more additional busesand bus bridges to which various additional components can be coupled.Similarly, a variety of alternate internal networks could be usedincluding, for instance, an internal network based on a high speedsystem bus with a memory controller hub and an I/O controller hub.Additional components may include additional processors, a CD ROM drive,additional memories, and other peripheral components known in the art.

In one embodiment, various functions of the present invention, asdescribed above, could be implemented using one or more hardware systemssuch as the hardware system of FIG. 12. Where more than one computer isused, the systems can be coupled to communicate over an externalnetwork, such as a local area network (LAN), an internet protocol (IP)network, etc. In one embodiment, one or more functions of the presentinvention as described above may be implemented as software routinesexecuted by one or more execution units within the computer(s). For agiven computer, the software routines can be stored on a storage device,such as permanent memory 1240.

Alternately, as shown in FIG. 13, the software routines can be machineexecutable instructions 1310 stored using any machine readable storagemedium 1320, such as a hard drive, a diskette, CD-ROM, magnetic tape,digital video or versatile disk (DVD), laser disk, ROM, Flash memory,etc. The series of instructions need not be stored locally, and could bereceived from a remote storage device, such as a server on a network, aCD-ROM device, a floppy disk, etc., through, for instance, I/O device(s)1250 of FIG. 12.

From whatever source, the instructions may be copied from the storagedevice into temporary memory 1220 and then accessed and executed byprocessor 1210. In one implementation, these software routines arewritten in the C programming language. It is to be appreciated, however,that these routines may be implemented in any of a wide variety ofprogramming languages.

In alternate embodiments, the embodiments of the present inventiondescribed above may be implemented in discrete hardware or firmware. Forexample, one or more application specific integrated circuits (ASICs)could be programmed with one or more of the above described functions.In another example, one or more functions of the present invention couldbe implemented in one or more ASICs on additional circuit boards and thecircuit boards could be inserted into the computer(s) described above.In another example, field programmable gate arrays (FPGAs) or staticprogrammable gate arrays (SPGA) could be used to implement one or morefunctions of the present invention. In yet another example, acombination of hardware and software could be used to implement one ormore functions of the present invention.

Thus, a novel power system configuration and a novel battery packconfiguration are described. Whereas many alterations and modificationsof the present invention will be comprehended by a person skilled in theart after having read the foregoing description, it is to be understoodthat the particular embodiments shown and described by way ofillustration are in no way intended to be considered limiting.Therefore, references to details of particular embodiments are notintended to limit the scope of the claims.

1. An apparatus comprising: an input power port; a power rail; a batteryunit; and a system charger voltage regulator (VR) to couple the inputpower port to the battery unit, and said battery unit to couple with thesystem charger VR and the power rail.
 2. The apparatus of claim 1wherein said system charger VR is to provide a regulated voltage signalwhen a power source is coupled to the input power port, said regulatedvoltage signal to simultaneously power both the power rail and thebattery unit.
 3. The apparatus of claim 2 wherein said battery unit isto provide a battery voltage signal to power the power rail when nopower source is coupled to the input power port.
 4. The apparatus ofclaim 3 wherein the regulated voltage signal and the battery voltagesignal have a common upper bound and a common lower bound.
 5. Theapparatus of claim 2 wherein the power source comprises a voltage fromone of an AC/DC converter, an external battery, a fuel cell, a solarpanel, and power over local area network.
 6. The apparatus of claim 1wherein the battery unit comprises: a battery pack port to couple to thesystem charger VR and to receive a battery pack; and a power sourceselector to selectively couple either the system charger VR to the powerrail or the battery pack port to the power rail.
 7. The apparatus ofclaim 6 wherein the system charger VR is to power the battery pack portto recharge a discharged battery coupled to the battery pack port. 8.The apparatus of claim 1 wherein the battery unit comprises: a pluralityof battery pack ports, each of the plurality of battery pack ports tocouple to the system charger VR and to receive a battery pack; and apower source selector to selectively couple any one of the systemcharger VR and the plurality of battery pack ports to the power rail. 9.The apparatus of claim 8 wherein the battery unit further comprises: abattery charging selector to couple between the system charger VR andeach of the plurality of battery pack ports, said battery chargingselector to selectively couple any one of the plurality of battery packports to the system charger VR.
 10. The apparatus of claim 1 wherein thepower rail extends beyond the battery unit to couple the system chargerVR to the battery unit
 11. The apparatus of claim 10 wherein the batteryunit comprises: a battery pack port to receive a battery pack.
 12. Theapparatus of claim 11 wherein the battery unit further comprises: aswitch to selectively couple the battery pack port to the power rail.13. The apparatus of claim 12 wherein, if the battery pack is coupled tothe battery pack port, said switch is to couple the battery pack port tothe power rail for either powering the power rail or charging thebattery pack.
 14. The apparatus of claim 11 wherein the battery packcomprises: a switch control port to receive a switch control signal fromthe battery pack port; a battery stack; and a switch to selectivelycouple the battery stack to the battery pack port based at least in parton the switch control signal.
 15. The apparatus of claim 10 wherein thebattery unit comprises: a plurality of battery pack ports, each toreceive a battery pack.
 16. A method comprising: generating a regulatedvoltage signal when a power source is available; providing the regulatedvoltage signal to simultaneously power both a power rail and a batteryunit; and providing a battery voltage signal to power the power railwhen no power source is available.
 17. The method of claim 16 whereinthe regulated voltage signal and the battery voltage signal have acommon upper bound and a common lower bound.
 18. The method of claim 16wherein the power source comprises a voltage from one of an AC/DCconverter, an external battery, a fuel cell, a solar panel, and powerover a local area network.
 19. The method of claim 16 wherein providingthe regulated voltage signal to power the battery unit comprises:recharging a discharged battery in the battery unit.
 20. A systemcomprising: a mobile computer; and a power apparatus for the mobilecomputer, said power apparatus comprising an input power port; a powerrail; a battery unit; and a system charger voltage regulator (VR) tocouple the input power port to the battery unit, and said battery unitto couple with the system charger VR and the power rail.
 21. The systemof claim 20 wherein said system charger VR is to provide a regulatedvoltage signal when a power source is coupled to the input power port,said regulated voltage signal to simultaneously power both the powerrail and the battery unit.
 22. The system of claim 21 wherein saidbattery unit is to provide a battery voltage signal to power the powerrail when no power source is coupled to the input power port.
 23. Thesystem of claim 22 wherein the regulated voltage signal and the batteryvoltage signal have a common upper bound and a common lower bound. 24.The system of claim 20 wherein the battery unit comprises: a batterypack port to couple to the system charger VR and to receive a batterypack; and a power source selector to selectively couple either thesystem charger VR to the power rail or the battery pack port to thepower rail.
 25. The system of claim 20 wherein the battery unitcomprises: a plurality of battery pack ports, each of the plurality ofbattery pack ports to couple to the system charger VR and to receive abattery pack; and a power source selector to selectively couple any oneof the system charger VR and the plurality of battery pack ports to thepower rail.
 26. The system of claim 25 wherein the battery unit furthercomprises: a battery charging selector to couple between the systemcharger VR and each of the plurality of battery pack ports, said batterycharging selector to selectively couple any one of the plurality ofbattery pack ports to the system charger VR.
 27. The system of claim 20wherein the power rail extends beyond the battery unit to couple thesystem charger VR to the battery unit
 28. The system of claim 27 whereinthe battery unit comprises: a battery pack port to receive a batterypack.
 29. The system of claim 28 wherein the battery pack portcomprises: a switch to selectively couple the battery pack port to thepower rail wherein, if the battery pack is coupled to the battery packport, said switch is to couple the battery pack port to the power railfor either powering the power rail or charging the battery pack.
 30. Thesystem of claim 28 wherein the battery pack comprises: a switch controlport to receive a switch control signal from the battery pack port; abattery stack; and a switch to selectively couple the battery stack tothe battery pack port based at least in part on the switch controlsignal.
 31. The system of claim 27 wherein the battery unit comprises: aplurality of battery pack ports, each to receive a battery pack.